package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisConstants;
import com.hmdp.utils.RedisData;
import org.apache.tomcat.jni.Time;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author 冀朝赛
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @Resource
    private CacheClient cacheClient;
    /**
     * 根据id查询商铺信息
     * 缓存穿透解决方案:缓存空对象
     *
     * @param id
     * @return
     */
    @Override
    public Result queryById(Long id) {
        //逻辑过期解决缓存击穿
        Shop shop = cacheClient.queryWithLogicalExpire(RedisConstants.CACHE_SHOP_KEY, id, Shop.class, this::getById, 20L, TimeUnit.SECONDS);

        //解决缓存穿透
        //Shop shop = cacheClient.queryWithChuanTou(RedisConstants.CACHE_SHOP_KEY, id, Shop.class, this::getById, 30L, TimeUnit.MINUTES);
        if (shop == null) {
            return Result.fail("商铺不存在");
        }
        return Result.ok(shop);
    }

    public Shop queryWithChuanTou(Long id) {
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(RedisConstants.CACHE_SHOP_KEY + id);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在,直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否是空值
        if (shopJson != null) {
            //返回一个错误信息
            return null;
        }
        //4.不存在,根据id查询数据库
        Shop shop = getById(id);
        //5.不存在,返回错误
        if (shop == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY + id, "", 2L, TimeUnit.MINUTES);
            return null;
        }
        //6.存在,写入redis,超时剔除
        stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop), 30L, TimeUnit.MINUTES);
        return shop;
    }

    /**
     * 根据id查询店铺信息
     * 缓存击穿的示例:利用互斥锁实现
     *
     * @param id
     * @return
     */
    public Shop queryWithPassThrough(Long id) {
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(RedisConstants.CACHE_SHOP_KEY + id);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在,直接返回
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中的是否是空值
        if (shopJson != null) {
            //返回一个错误信息
            return null;
        }
        //4.实现缓存重建
        String lockKey = RedisConstants.LOCK_SHOP_KEY + id;
        //4.1获取互斥锁
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2判断是否获取成功
            if (!isLock) {
                //4.3失败,休眠并重试
                Thread.sleep(50);
                return queryWithPassThrough(id);
            }
            //4.4成功,根据id查询数据库
            shop = getById(id);
            //模拟重建延时
            Thread.sleep(200);
            //5.不存在,返回错误
            if (shop == null) {
                //将空值写入redis
                stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY + id, "", 2L, TimeUnit.MINUTES);
                return null;
            }
            //6.存在,写入redis,超时剔除
            stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(shop), 30L, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放互斥锁
            unLock(lockKey);
        }

        return shop;
    }

    private static  final ExecutorService CACHE_REBUILD_EXECUTOR= Executors.newFixedThreadPool(10);
    /**
     * 缓存击穿的示例:利用逻辑过期实现
     */
    public Shop queryWithLogicalExpire(Long id) {
        //1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(RedisConstants.CACHE_SHOP_KEY + id);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.存在,直接返回
            return null;
        }
        //4.命中,需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.1判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //未过期,直接返回店铺信息
            return shop;
        }
        //5.2 已过期,需要缓存重建

        //6.缓存重建
        //6.1获取互斥锁
        String lockKey=RedisConstants.LOCK_SHOP_KEY+id;
        boolean isLock=tryLock(lockKey);
        //6.2判断是否获取锁成功
        if(isLock){
            //6.3成功,开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //重建缓存
                    this.saveShopRedis(id,20L);
                }catch (Exception e){
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }

        //6.4 返回过期的商铺信息

        return shop;
    }

    /**
     * 逻辑过期预热
     *
     * @param
     * @return
     */
    public void saveShopRedis(Long id, Long expireSeconds) throws InterruptedException {
        //1.查询店铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        //封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //写入redis
        stringRedisTemplate.opsForValue().set(RedisConstants.CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    //获取锁
    public boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

     //释放锁
    public void unLock(String key) {
        stringRedisTemplate.delete(key);
    }

    /**
     * 更新商铺信息
     *
     * @param shop
     */
    @Override
    @Transactional
    public Result updateShop(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除缓存
        stringRedisTemplate.delete(RedisConstants.CACHE_SHOP_KEY + id);
        return Result.ok();
    }
}
